Flattening and kinematics of the galactic halo

The Jeans equations are used to study the Galactic halo. Relations are derived between the axial ratio q of the metal-poor halo, the axial ratio |q̃| of the dark halo, and the local velocity ellipsoid of metal-poor halo stars. Comparison with observational data implies that (i) neither models in which the principal axes of the velocity ellipsoid align with cylindrical coordinate axes, nor models in which they align with spherical coordinate axes can be ruled out by the presently available observational data; (ii) if the principal axes of the velocity ellipsoid align with cylindrical coordinate axes, then |q<0.67;| (iii) if the metal-poor halo and the dark halo have the same axis ratio, then |q=q̃> 0.53;| (iv) the axial ratio of the dark halo must satisfy |q̃> 0.34|⁠.